Italian rider Ivan Basso has withdrawn from the Tour de France after revealing he has testicular cancer.

"We discovered this two hours ago. I have to stop," the former Giro d'Italia winner, 37, told a shocked news conference on Monday.

Basso was set to be one of Alberto Contador's key lieutenants in the mountains over the next two weeks.

He caught his groin in a crash on stage five and the cancer was discovered in a check-up on the race's first rest day.

Tinkoff-Saxo team-mate Contador was in tears as he sat next to Basso during his announcement.

Basso, who will travel to Italy to undergo surgery as soon as possible, twice finished on the podium during Lance Armstrong's long reign at the Tour and many, including Armstrong, expected him to follow the American on to the top step when he retired in 2005.

Testicular cancer - facts

It usually affects men between the ages of 15 and 49

It is relatively uncommon, accounting for 1% of all cancers that occur in men

It is one of the most treatable types of cancer. More than 96% of men with early-stage testicular cancer will be completely cured

Several footballers have recovered from testicular cancer, including former Newcastle midfielder Jonas Gutierrez, former Bolton and Celtic defender Alan Stubbs, ex-Arsenal and West Ham striker John Hartson, former Millwall striker Neil Harris, ex-Northampton goalkeeper Matt Duke and ex-Tottenham and Chelsea defender Jason Cundy

But Basso got caught up in the Spanish Operation Puerto doping scandal and eventually admitted to the intention to cheat. He was given a two-year ban in 2007.

The Italian climber, who owns a blueberry farm in Lombardy, has claimed five top-10 finishes in Grand Tours since his return to the sport, including a Giro win in 2010.

He is also one of the friendliest and more relaxed members of the professional peloton so this news will be greeted with considerable dismay.

His diagnosis will also increase the focus on Armstrong's arrival in France next week to ride two stages of the Tour with ex-England footballer Geoff Thomas - a day ahead of the race - to raise money for a cancer charity.

Armstrong recovered from life-threatening testicular cancer earlier in his career to win the seven Tour titles he was eventually stripped of for his doping activities.